In a radiotelephone, a reference crystal may be used to generate a clock signal for a processor of the radiotelephone. Harmonics of the clock signal, however, may interfere with the radio signals received at the radiotelephone. With a 13 MHz clock signal, for example, the 72nd and 73rd harmonics of the 13 MHz clock signal may interfere with communications provided over one or more channels of the GSM (Global System For Mobile Telecommunications) 900 MHz standard. For example, the 72nd harmonic at 936 MHz may interfere with GSM channel 5, and/or the 73rd harmonic may interfere with GSM channel 70. Because inputs/outputs to/from the radiotelephone processor are provided between the processor and other elements (e.g., a keypad, a display, a speaker, a microphone, etc.) of the radiotelephone, it may be difficult to provide adequate shielding with respect to the clock signal and/or harmonics thereof.